Nevada’sNevada’s Mule Deer Population Dynamics: Issues and Influences Nevada's Mule Deer Biological Bulletin No.14 Mule Deer Population Dynamics: Issues and Influences By Tony Wasley NDOW Big Game Biologist This document is the result of studies undertaken with Federal Aid in Fish and Wildlife Restoration funds under Pittman-Robertson Projects. August 2004 Nevada's Mule Deer Biological Bulletin No.14 I State of Nevada Kenny C. Guinn, Governor Department of Wildlife Terry R. Crawforth, Director Game Bureau Gregg Tanner, Chief Board of Wildlife Commissioners Tommy Ford, Chairman / Las Vegas Chris MacKenzie,Vice Chairman / Carson City Clint Bentley / Las Vegas Bill Bradley / Reno James Jeffress / Lovelock Ron Lurie / Las Vegas David McNinch / Reno Eric J. Olsen / Fallon Mike Riordan / Jiggs _______________________________________________________________________________________________________________ Cover Photo: Buck and doe mule deer standing on weed-infested winter range, a site once occupied by sagebrush and other native vegetation. The Nevada Department of Wildlife receives funds from Federal Aid in Fish and Wildlife Restoration Acts. Federal and State law state that there shall be no difference in the treatment of individuals because of race, color, creed, religion, nation origin, sex or disability. Anyone receiving alleged discriminatory treatment in any Department program, activity or facility should report it to either: Director U.S. Fish & Wildlife Service Nevada Department of Wildlife Department of the Interior 1100 Valley Road 18th & C Streets Reno, NV 89512 Washington D.C. 20240 Nevada's Mule Deer Biological Bulletin No.14 II Table of Contents ACKNOWLEDGEMENTS . 1 INTRODUCTION . 2 EVOLUTION AND NATURAL HISTORY . 2 HISTORY OF NEVADA’S MULE DEER . 2 MULE DEER STATUS . 4 MULE DEER DECLINE . 5 POOR BODY CONDITION . 7 DIGESTIVE PHYSIOLOGY AND DIET . 7 Habitat Factors DEGRADED HABITAT . 9 PLANT AGE AND SENESCENCE . 10 PINYON JUNIPER ENCROACHMENT . 11 OVERGRAZING BY LIVESTOCK . 12 WILDFIRE AND INVASIVE SPECIES . 14 TYPE CONVERSIONS . 15 INTERRELATED RANGE FACTORS . 16 CYCLIC PHENOMENA . 17 HUMAN POPULATION FACTORS . 22 Factors Reducing Animal Condition and Survivorship HUMAN INDUCED FACTORS . 23 CLIMATIC EXTREMES . 25 DISEASE . 25 PREDATION . 26 Other Issues HARVEST AND ANTLER DEVELOPMENT . 29 COMPETITION . 32 SUMMARY - THE WHOLE STORY . 37 BIBLIOGRAPHY AND LITERATURE CITED . 39 APPENDICES . .AI Nevada's Mule Deer Biological Bulletin No.14 III List of Figures and Appendices Figures Figure 1 Approximation of Nevada’s Mule Deer Population Dynamics Late 1800s - 2003: . 3 Figure 2 Nevada Buck Harvest 1929 - 2003: . 3 Figure 3 10 Year Average of Nevada Buck Harvest 1934 - 1998: . 4 Figure 4 Identification of Mule Deer Population Increase and Decrease Phases: . 4 Figure 5 Spring Fawn Ratios 1973 - 1988 and 1989 - 2004: . 6 Figure 6 Three Year Average of Total Annual Precipitation Elko, NV 1890 - 2003: . 17 Figure 7 Spring and Summer Precipitation at Elko, NV 1950 - 2002 : . 18 Figure 8 Monthly Precipitation for Jiggs, NV 1981- 1986 and 1991 - 1996: . .18 Figure 9 Monthly Precipitation for Elko, NV 1981- 1986 and 1991 - 1996: . 19 Figure 10 Average Monthly Summer Precipitation for Elko, NV 1890 - 2003: . 19 Figure 11 Average Monthly Summer Precipitation at Orovada, NV 1976 - 1985 and 1994 - 2003: . 20 Figure 12 Average Monthly Summer Precipitation at Austin, NV 1976 - 1985 and 1994 - 2003: . 20 Figure 13 Total Summer Precipitation (three year average) at Gibbs Ranch, NV 1958 - 2002: . 20 Figure 14 Differences in Photosynthetic Activity Between 1985 and 2000 for Area 7: . 21 Figure 15 Relationship Between Nevada’s Statewide Mule Deer Population Estimate and Summer Precipitation: . 21 Figure16 Regression of Mule Deer Population Estimate and Summer Precipitation: . 21 Figure 17 Photo of Housing Development on Mule Deer Winter Range: . .22 Figure 18 Photo of Deer Caught in Wire Fence: . 23 Figure 19 Photo of Winter Related Mortalities of Mule Deer: . 25 Figure 20 Coyote Take and Mule Deer Buck Harvest 1969 - 2002: . 27 Figure 21 Coyote Take, Mule Deer Buck Harvest, and Summer Precipitation 1969 - 2002: . 27 Figure 22 Coyote Harvest and Mule Deer Spring Fawn Ratios 1976 - 2002 : . 28 Figure 23 Buck and Doe Harvest 1951 - 2003: . 30 Appendices Appendix I Statewide Map of Mule Deer Distribution and Associated Habitats: . A1 Appendix II Flow Chart Depicting Issues and Influences Affecting Mule Deer Population Dynamics: . A2 Appendix III Additional Mule Deer Readings: . .A3 Nevada's Mule Deer Biological Bulletin No.14 IV Acknowledgments I am grateful for the knowledge, support, and advice that I’ve received from numerous individuals through- out this process. The opportunity to develop this document was only possible through the direction and support of Director Terry Crawforth and Deputy Director Gene Weller. Game Bureau Chief Gregg Tanner and Big Game Program Coordinator Mike Cox assisted with data, records, and historical information. Special thanks go to the many NDOW biologists and staff who shared experiences, philosophies, and wisdom and who also provided valuable comments to improve the manuscript. Management assistants Dar Jan Kerr and Tabby Mays and volunteer Marcial Evertsen provid- ed key support activities. The Northern Nevada Chapter of the Safari Club International provided funding for acquisition and analysis of satellite imagery. Bethany Bradley of Brown University’s Remote Sensing Lab performed the image analysis. Retired biologists Joe Williams, Mike Hess, Bob McQuivey, Merlin McColm, Don King, and Duane Erickson provided valuable advice and perspectives. Photo credits go to a number of NDOW biologists including Ken Gray, Craig Mortimore, and John Elliott. Funding for this project was derived from tag and license revenues and grant assistance provided by the Pittman-Robertson Federal Aid in Wildlife Restoration program. Nevada's Mule Deer Biological Bulletin No.14 1 Introduction Mule deer are the primary big game species in had read about in the journals of a Canadian trader Nevada. Mule deer are the most numerous, most wide- named Charles Le Raye. Le Raye had been held captive spread (appendix 1), and most recognizable of Nevada’s by the Sioux for nearly 14 years. In his journals, Le Raye wild ungulates. Mule deer populations in Nevada have referenced “mule deer”and provided a physical descrip- fluctuated greatly over the past 150 years. After reaching tion. Based on the physical descriptions supplied by Le what was arguably an all-time population high in the late Raye, Rafinesque derived the scientific name. 1980s, mule deer have spent the last 15 years struggling History of Nevada s Mule Deer to maintain numbers roughly half of what existed 15 years ago. The suspected causes and culprits contribut- Most people consider current mule deer popula- ing to mule deer losses are abundant. This biological bul- tions as “low”or “down”. As with any population, the letin endeavors to address not only the biological factors highs and lows are only high or low relative to some his- surrounding the recent decline of mule deer in Nevada, torical reference point. In order to determine whether but the biology of mule deer population dynamics in the current status of mule deer is “up”or “down,”it is nec- Nevada by thoroughly examining, the evolution and natu- essary to evaluate the complete history of mule deer pop- ral history of mule deer, the history of mule deer in ulation dynamics in Nevada. Nevada, and the risks, threats, and issues facing mule deer. Accurate historical data on mule deer popula- Additionally,the history and philosophies of harvest tions is sparse. Although trappers and pioneers traveled to strategies will be explored. and through Nevada as early as 1824, true mule deer pop- Evolution and Natural History ulation census data have only been collected since the early 1950s and intensively only since 1976. Despite the The mule deer is a native of North America. The lack of early census efforts, there are still some useful indi- species originated on this continent from a primitive deer cators of early mule deer numbers. that came from Asia probably well over a million years Although there are numerous sources of mule deer ago. Mule deer most likely evolved in the rugged moun- population data,there are only four main sources of data. tains of the West where it developed numerous adapta- Each of the four sources covers four different time intervals. tions to the frequently inhospitable environment. The Mule deer presence and absence data from roughly 1825 - mule deer is an animal of broken forests and mountain 1850 were recorded quite well by the early pioneers. Many brush zones, dependent on Mother Nature and other of the early trappers and pioneers kept detailed journals and environmental forces to provide the disturbances that diaries of their daily activities,which included observations of stimulate the production of favorable forage and wildlife and wildlife sign (i.e.tracks around water sources). cover species. These diaries and journals have been evaluated thoroughly The mule deer was first described by Lewis by multiple individuals and any and all references to wildlife and Clark in 1804. They gave it the name “mule deer”on have been recorded and evaluated. account of the length of its ears. The scientific name Mule deer data from approximately 1850 - Odocoileus hemionus (Odocoileus means hollow tooth 1900 are recorded quite thoroughly in the numerous and hemionus means half-mule) came several years later